Steam generator



, May 26, 1936. w. ABEND RO TH Re. 19,977

STEAM GENERATOR Original Filed 001:. 23; 1951 2 Sheets-Sheet 1 1,299220,: memmewm.

May 2.6, 1936. w. ABENDROTH 19977 STEAM GENERATOR Original Filed Oct.2;, 1931 2 Sheets-Sneet 2 Reiuuecl,May-26,-1936 UNITED STATES swamcnrmaaron PATENT orrica In Germany October 24, 1930 14 Claims. (Cl.122-449) My invention relates to improvements in steam generators andmore particularly to an arrangement in critical pressure steamgenerators.

By a critical-pressure steam generator is to be understood a steamgenerator in which the working medium in being converted into steampasses from the liquid to the gaseous state at the critical pressure andcritical temperature. There is no a surface of separation betweentheliquid and the vapor, and the latent heat is zero.. The pressure israised by means of a pump. The critical-pressure steam generator isconstructed without any drums and consists merely of a tube, or tubes,through which the working medium is forced by a pump. The steamgenerator is' subdivided. into two parts, viz, into one part in whichthe heat is transmitted by radiation (radiation heating part) and asecond part, in which the heat is transmitted by contact of the hotgases with the tubes (contact heating part). structions of thecritical-pressure steam. generator, the conversion zone, in which theworking medium changes its form from a liquid to a vapor, lies withinthe radiation heating part.

At high degrees of heat in the radiation heating part it has been foundthat when disturbances occur they do not do so. in the part having thehighest temperatures but in regions of somewhat lower temperature andparticularly close to, or in,

' the zone in which the conversion of the liquid to vapor takes place.The reasons for this are not yet entirely known. It can, however, beassumed that it is caused by some disturbance in the trans mission ofthe heat. The problem, therefore, arose of altering the construction ofthe criticalpressure steam generator in such a manner as to avoid thedisturbances in the conversion zone. The solution found was to give suchproportions to the tube system that the zone in which the liquid workingmedium is converted into vapor lies in the contact heating part. Theconversion zone is, therefore, withdrawn from the influence of theradiating heat. The experience gained in .service with critical-pressuresteam generators constructed in that manner shows that the disturbanceswith whichone heretofore had to contend are thereby eliminated. Thefurther'heat transmission necessary for obtaining the desired finalcondition of the steam need not take place in the contact heating part,but the. tube system may be led back into the radiation heating part.

The transfer of the conversion zone into the contact heating partrenders a further development of the critical pressure steam generatorpossible. It is a well known fact that the working of tubular steamgenerators of the water-tube type with forced watercirculation'is veryliable to be affected, if the water used is not sufllciently pure. Inthe course of time deposits of scale are formed in the tubes and reducethe section of In the previous con-- passage. The formation of scale isa consequence of the concentration of the lye.

When using critical-pressure steam generators,

' it is in many cases possible to provide feed water of the desiredpurity but special cases may occur in which undesirable impurities findtheir way into the feedwater. That might, for instance, be the case ifthe condenser leaks so that the cooling water mixes with the condensate.The

concentration of the lye is not the same at all '1 tures of the steamgenerator working at the critical pressure, a way can be found to makeis possible forthe' enriched lye to be removed, consisting in theinsertion of a wider tube in the conversion zone. The ideais to insertin the path of flow a small drum or header which, owing to the highpressures, can only have small dimensions and may be regarded as awidening of the tube. The steam generator will generally be so' operatedas to cause a slight overheating of the steam in the widened part of thetube. If it is now desired to drain off the concentrated lye,

' the temperature of the gases in the contact heat ing part is reduced,for example, by diminishing the supply of fuel. Consequently thetempera- 4 two in the widened tube also drops. But, as the criticalpressure of the contents of the tube is maintained by the pumpindependently of the obtaining temperature, the tube fills with a mediumatcritical pressure but at a temperature below the critical, 1. e. itfills with liquid. Now, since, as mentioned above, the concentration 'ofthe lye increases the more it approaches the evap- 4o oration zone; thegreatest concentration of the lye is just attained when the liquidenters the widened tube. If, therefore, the latter is provided with anemptying device, the concentrated lye can be removed from the steamgenerator. By increasing the heat supplied, the temperature is againraised and the widened tube is made to be re-situated behind theconversion zone in the steam current. Tests have shown that the widenedtube should have such proportions that the E0 velocity of flow in samedoes not exceed 0.5 metres per second. The widened tube isadvantageously so placed as not to. be within the influence of the fluegases.

As in tubular steam generators with forced water circulation theindividual tubesccnnected in parallel are joined up to collectors toobtain a good mixing of their contents and are from there .led back intothe steam generator, it is lmder circumstances possibleto provide one ofthese exenriched lye, if said collector is situated in a region in whichthe temperature is capable'of being reduced below the critical byreducing the salts temperature of the flue gases.

The device according to the invention distinguishes'from the ordinaryboiler drum by being continually in the steam current and is only atcertain times filled with the lye to be removed,

whereas the usual boiler drum serves primarily for the reception ofliquids.

The invention will now be described with reference to the accompanyingdrawings of which:

Figure 1 is an elevation partly in section of one form of the invention.

Figure 2 is a view similar to to Figure 1 showing a modification. t

Figure 3 shows in cross section one of the throttling'devices employedin Figure 2. I

Figure 4 shows 'a throttling disk employed in the modificationillustrated in Figure 2.

Figure 5 shows an alternative form of sludge tank which may be employedin the modification illustrated in Figure 2.

Figure 1 shows a steam generator heated, for example, by a furnaceprovided with a chain grate stoker I and containing a combustion chamber2 and two flue-gas chambers 3a. and

3b. The flames from the fire on the chain grate I first rise in thecombustion chamber 2, from where the flue gases from the flames'afterbeing diverted at the upper end of the combustion chamber descend in thechamber 3a. At the bottom end of the chamber 3a they are again divertedand after having risen in the chamber 3b, they are finally drawn off bythe blower l and conveyed into the chimney 5. In the chambers 2,

3a and 3b are coiled tubes 6, I, B, 9, III and II,

through which by means of a pump I! the working medium is forcedsuccessively in a continuous flow'and at a gradually rising temperature.The

generated steam'is conveyed through the pipe line I3 to'thesteam-consuming machine or ap-.

paratus. As the coiled tubes'8 and M are directly'swept by the flamesfrom the fire on the grate, the heating of these parts of the tube is,of course, brought about mainly by radiation, whereas the coiled tubes8, I, 9 and II located in the chambers in and 3b are heated throughbeing in-contact with the hot flue gases. When the steam generator is inoperation, the working medium, which the pumpv presses successivelythrough the tube coils a, 1, 1:, 9,10 and u, remains in a liquid stateas long as the critical temperature corresponding to the criticalpressure is not yet reached. As soon as that is the case, the liquidchanges into steam. This zone, in which the conversion of the liquidinto steam takes place, issituated according to the inventionapproximately within that part of the tube which is indicated by thebracket and the reference numeral ll.

Furthermore it will be seen from the drawings that behind (seen in thedirection of flow of the working medium) said conversion zone I4 awidening IS in tubular form is provided.

As long as the steam generator is in' normal operation, the conversionzone I4 is in the chamber In, heated by the flue gases, at a-pointbefore the widening l5 of the tube, in the direction'of flow. To removethe sludge, or mud in the said way according to the invention, all thatis necessary is to vary the speed of the two motors l8- and. I! by meansof the two regulators l5 and II in such a manner as to reduce thetemperamay? ture of the flue gases until the liquid advances into thewidened tube l5. As already mentioned above, the liquid thereby made toenter the widened tube I5 is particularly enriched with This liquid canthen be blown out through the pipe 25 and the valve 2 I. After theconcentrated lye has been removed from the steam generator in thismanner the conversion zone is made to return to a point before thewidened tube in the chamber 30. This is done simply by increasing thetemperature of the flue gases. Fig. 1 also shows an expedient manner ofconducting the tubes after they have left the sludge-removing zone, i.e. the widened tube. As illustrated, the

the invention to steam generators having a plu rality of tubes connectedin parallel as shown on the drawings.

In the foregoing the removal of the sludge was described as beingpossible after the heating of the steam generator has been reduced.There is, however, also a second way of removing the sludge, consistingnot in reducing the heating of the steam generator but in increasing thequantity of working medium fed into same. In this case the conversionzone is also shifted in the direction of flow of the working medium; Ac-

cording to the invention this fact is made use of for example, in steamgenerators having a pinrality of tubes connected in parallel,'byprovidzone in each tube and by increasing the quantity of flow throughthe tube line from which the sludge is to be removed. The conversionzone is concentrated lye can be blown off through the sludge removingpipe. Furthermore according to 35 ing a sludge-removing pipe behind theconversion the invention a device, the action of which is 7 similar tothat of a check valve and which during the removal of the sludgeprevents the working medium, from flowing back from the tubes not beingcleaned at the moment, is provided behind the point at which thesludge-removing pipe is joined on to each tube.

The manner in' which the sludge is removed from the tube, or tubes, willbe more fully described in the following with reference to Figs. 2 to5'of the accompanying drawings. As shown, the heated surfaces of the.steam generator consist solely of tubes.

The latter are located partly in a combustion chamber 5| and partly inthe gas flues 52 and 53, so that they are heated in part by radiationandin part by contact. The steam generator is, by

way of example, provided with a chain grate stoker 54. The hot gasesproduced by the flames are first diverted in the upper part. of thechamber 5| and enter the chamber 52 from which, afterhaving been againdiverted at the bottom of this chamber, they pass through the secondflue '53 and leave the same 'at the top.- The working medium is pressedthrough the tubes, for example, by means of a pump 55 driven by a regu-I path. It is introduced by the main pipe 51 and-is lines.

working medium is repeatedly mixed in headers and again distributedintofurther parallel tubes.

On its way it passes through the headers 59 to 69. The heating surfaceshould be so proportioned that the zone within which the liquid isconverted to vapor lies approximately at the place indicated by thebrackets and the reference numerals Ill, H, and 12. Before the header 6!which is situated behind the conversion zone, as seen in the directionof flow of the working medium, are inserted devices I3, 14, I5respectively, for throttling return currents in each of the tube Thearrangement of the throttling devices 13, II and I5 and their shape isto be seen particularly in Fig. 2. By a device for throttling returncurrents is to be understood a nozzle so fitted in the path of flow thatin normal operation the working medium enters the nozzle at its smallestsection and leaves it at its largest section. The conversion of pressureinto speed which takes place at the narrowest part of the nozzle is withthis arrangement nullified by the diffusing action of the divergingpart. In normal operation of the steam generator the nozzle built-in inthis manner would cause but an inconsiderable lossof pressure. This is,however, not the case, it the direction of flow is reversed, i. e. ifthe working medium enters the nozzle at its largest section and leavesit at its narrowest section. In this case no part acting as a diifuserfollows the narrowestsection, so that with this direction of flow thenozzle has a strong throttling effect. This fact is made use of in themanner further described below.

As will be seen in the drawings, sludge-removing pipes 19, 80 and 8! arejoined to each of the tubes l6, l1 and 18 at a point situated betweenthe conversion zone and the throttling devices 13. ll, 15. At the end ofthese sludge-removing pipes are provided throttling disks '82, 83 and 84and closing valves 85, 86 and 81.

If sludge is to be removed from, for example, the tube 16, the procedureis as follows: First the conversion zone I within which the liquidchanges into steam has to be shifted far enough for the liquidcontaining sludge or salts to reach at least the point where thecorresponding sludgeremoving pipe Ill leaves the tube.

In the present case'it is assumed that the displacement of theconversion zone is to take place through increase of the quantity ofworking thedium flowing through the tube in question. For the sake ofsimplicity, we will take a concrete case and assume that for displacingthe conversame time at which the delivery of the pump is increased, theclosing valve 85 is opened to blow off the lye. If during this procedurethe quantity of steam generated is to remain unaltered, the valve 85will have to be opened just far enough to allow 1/3 Q to escape throughthe sludge-removing pipe 19. To ensuresteady working condi-- tions, Isuggest according to my invention placing 'a throttling disk 82 in frontof the valve 85, which, evenif the latter is opened to its fullestextent, limits automatically the quantity of flow to about at thepredetermined pressure of the pump. Fig. 4 shows this throttlingarrangement on an enlarg'ed scale. When by this means a suflicientquantity of liquid has been removed from the tube 16, the valve as isclosed and simultaneously one of the valves 8 or 81 opened, or in casethe removal of the sludge from the two tubes H and I8 has already beencarried out, the delivery of the pump is at once reduced to the normalamount Q. In this connection the importance of the devices forthrottling return currents 13, N and 15 becomes obvious. If thesethrottling devices were not provided, a certain amount of working mediumwould flow back from the header 65 during the time the sludge is beingremoved from one of the tubes. Since, as described above,

the nozzle, or throttling device, is so fitted as to prevent to aconsiderable degree the working medium from flowing back, the quantityof working medium fed'to the tubes situated beyond the header 65 ispractically the same during the removal of sludge as in normaloperation.

Fig. shows that the lye blown out when removing the sludge can becollected in a closed tank, from which the vapor, .or the steamdeveloped when concentrating the lye through additional heating, may beconveyed to, and utilized in, a low-pressure steam consumer.

I claim as my invention:

".1. A vapor generator comprising a furnace, a

heating surface formed of tubes, a part of said heating surface being solocated as to absorb mainly radiated heat and a part so located as toabsorb heat transmitted mainly by contact, a pump serving to force theworking medium through the tubes in the radiation heating part and thecontact heating part at at least critical pressure in continuous flowand with constantly increasing temperature, said tubes being. sodimensioned that the zone in which the working medium is converted froma liquid to a vapor is situated in the contact heating part.

2. A vapor generator comprising a furnace, a heating surface formed oftubes, 9. part of said heating surface being so located as to absorbmainly radiated heat and a part so located as to absorb heat transmittedmainly by contact, a pump serving to force the working medium throughthe tubes in the radiation heating part and the contact heating part atat least critical pressure in continuous flow and with constantlyincreasing temperature, said tubes being so dimensioned that the zone inwhich the working medium is converted from a liquid to a vapor issituated in the contact heating part, and. at least a part of the tubeslocated behind the conversion zone, in the direction of flow of theworking medium, being led back into the radiation heating chamber.

3. A vapor generator comprising a furnace, a heating surface formed oftubes, a part of said heating surface being so located as to absorbmainly radiated heat and a part so located as to absorb heat transmittedmainly by contact, a pump serving to force the working medium throughthe tubes in the radiation heating part and the contact heating part atat least critical pressure in continuous flow and with constantlyincreasing temperature, said tubes being so dimenlionedthat the zone inwhich the working medium is converted from a liquid to a vapor issituated in the contact heating part, and a widened tube provided with adevice for removing impurities, said widened tube being with respect'tothe direction of flow of the working medium situated behind theconversion zone.

4. A vapor generator comprising a furnace, a heating surface formed oftubes, a part of said heating surface being so located as to absorbmainly radiated heat and a part so located as to absorb heat transmittedmainly by contact, a pump serving to force the working medium throughthe tubes in the radiation heating part and the contact heating partatat least critical pressure in continuous fiow and with constantlyincreasing temperature, said tubes being so dimensioned that the zone inwhich the working medium is converted from a liquid to a vapor issituated in the contact heating part, and a widened tube provided with adevice for letting out impurities, said widened tube being with respectto the direction of fiow of the working me dium situated behind theconversion zone and withdrawn from the influence of the fiue gases.

5. A vapor generator comprising a furnace, a, heating surface formed oftubes, a part of said heating surface-being so located as to absorb,mainly radiated heat and a part so located as to absorb heat transmittedmainly by contact, a pump serving to force the working medium throughthe tubes in the radiation heating part and the contact heatingpart atat least critical pressure in continuous fiow and with constantlyincreasing temperature, said tubes being so dimensioned that the zone inwhich the working medium is converted from'a liquid to a vapor issituated in the contact heating part, at least a part of the ..tubeslocated behind the conversion zone, in the direction of flow of theworking medium, being led back into the radiation heating chamber, andat least one collecting header situated, with respect to the directionof,

flow of the-working medium, behind the conversion zone, the tubes comingfrom the conversion zone and led back to the radiation chamber beingjoined up to said header, said header being provided with a device forremoving impurities.

6. A vapor generator comprising a furnace, a

heating surface formed of tubes, a part of said heating surface being solocated as-to absorb mainly radiated heat and a part so located as toabsorb heat transmitted mainly by contact, a r

pump serving to force the working medium through the tubes in theradiation heating part and the contact heating part at at least criticalpressure in continuous fiow and with constantly increasing temperature,said tubes being, so dimensioned that the zone in which the work ingmedium is converted from a liquid to a vapor is situated in the contactheating part, and a pipe for removing sludge and capable of being closedjoined to each tube behind the conversion zone with respect to thedirection of flow of. the working medium, said tubes being then joinedup to a common header, a member offering a higher resistance to the flowof working medium from the header to the point at which the sludgeremoving pipe is joined up than to the flow in contrary direction beinginserted in each tube between the header and the point at which thesludge removing pipe is joined up.

'I. A vapor generator comprising a furnace, a heating surface formed oftubes, a part of said heating surface being so located as to absorbmainly radiated heat and a part so located as to absorb heat transmittedmainly by contact,

,a pump serving to force the working medium .is situated in the contactheating part, a pipe for removing sludge and capable of being closedjoined to each tube behind the conversion zone with respect to thedirection of fiow of the working medium, a throttling member inserted inthe sludge-removing pipe, said tubes being joined up to a common header,a member offering a higher resistance to the flow of working medium fromthe header to the point at which the sludge-removing pipe is joined upthan to the flow in contrary direction being inserted in, each tubebetween the header and the points at which the sludge-removing pipe isjoined up.

8. A vapor generator comprising a furnace, said furnace including firstand second chambers, combustion means providing a flame for the firstchamber and for passage of gaseous products of combustion from the,first chamber and through the second chamber, a heating surface formedof tubes, a part of said heating surface being located in the firstchamber so as to absorb mainly radiated heat and a part being lo- 'catedin the second chamber so as to absorb heat transmitted mainly bycontact, a pump serving to force the working medium to pass throughtubesof the radiation heating part in the first chamber and then throughtubes of the contact heating part in the second chamber, said workingmedium flowing continuously under pressure through the heating surfacewith continuous absorption of heat in order to continuously increase theheat content thereof, the .tubes of the heating surface being sodimensioned and arranged, with respect to operation of said combustionmeans and of said pump, that the zone in which conversion of the mediumfrom the liquid to the vapor state occurs and is accompanied by highconcentration of scale-forming impurities is situated in the part of theheating surface located in said second chamber.

9. A vapor generator including a furnace, said furnace comprising aplurality of vertical parallel chambers including first and secondchambers, combustion means providing a flame for the first chamber andfor passage of gaseous products of combustion from the first chamber Iand through the second chamber, heating surface formed of tubes andhaving parts thereof arranged in said chambers and includinga first partlocated in the first chamber so as to absorb mainly radiant heat and asecond part located in the second chamber so as to absorb heattransmitted mainly by contact, a pump for forcing working medium to flowin series through the parts of the heating surface and the parts of theheating surface being connected so that medium fiows in sequence throughsaid first and second parts, the working medium flowing continuously andunder pressure, through the parts of the heating surface with continuousabsorption of heat so as to increase the heat content thereof, the tubesof said heating surface being so dimensioned and arranged, with. respectto operation of said combustion means andof said pump, that the zone inwhich conversion of the medimnfrom theliquidtothevaporstate'cursandisaceompaniedbyhighconcentration 1 of scale-forming impuritiesis located in .secondpartinthesecondchamber.

' products ofcombustion from the first chamber and through thesecondchamber; heating surface formed of tubes and having parts thereofarranged in the chambers and including a first'partlocatedinthefirstchambersoastoabsorb mainlyradiant' heat, a secondpart in the second chamber so as to abwrb mainly contact heat-andathirdpartinone ofthechambersand located in the path of heating gasflow between the first and second parts; 'a pump for forcing workingmedium to fiow in series through the parts of the heating surface andthe parts of the-heating surface being so connected that the mediumflows in sequence through the first, second, and third parts of theheating surface and the medium flowing continuously under pressure withcontinuous absorption of heat in order to continuously increase the heatcontent thereof; the tubes of said first, second, and third parts of theheating surface being so arranged and dimensioned, with respect tooperating conditions of said combustion means and of said pump, that thezone in which conversion of themedium from the liquid ,to the vaporstate'occurs and is accompanied by high concentration or scaleformingimpurities is located in the second part of the heating surface arrangedin said second chamber. li. A vapor generator comprising a furnace I aheating surface'formed of tubes, a first part .of said heating surfacebeing so located in the furnace as to absorb mainly radiated heat and asecond part thereof being so located as to abv sorb heat transmittedmainly by contact, a pump serving to force the working medium to passthrough tubes of the first part of said heating surface and then throughtubes of the second part thereof in continuous flow and with continuousabsorption of heat in order to continuously increase the heat content ofsaid medium, the tubes of said heating surface being so dimensioned andarranged that the zone in which 3 conversion of medium from the liquidto the vapor state occurs and is accompanied by high concentration ofscale-forming impurities is located in said second part of the heatingsurface, said second part of the heating surface including a pluralityof tube means arranged for parallel flow of medium therethrough, meansproviding for removal of impurity concentrations from each of the tubemeans and capable of selective operation so that concentrations mayberemoved from said tube means one at a time while maintaining theremainder of said tube means in normalgenerator operation, and meanseffective to resist back flow in the tube means when impurityconcentrations are being removed therefrom.

12. A vapor generator comprising a furnace,

a heating surface formed of tubes, a first part of said heating surfacebeing so located in the furnace as to absorb mainly radiated heat and asecond part being so located as to absorb heat transmitted mainl bycontact, a pump serving to force the working medium to pass throughtubes of thefirst part of said heating surface ,to absorb mainly, highintensity flaw and w th Manicures-+- centration of scale-formingimpm'ities is located in said second part of the heating surface, saidsecondpartoftheheating surface includinga' plurality of tube meansarranged for parallel fiow of medium therethrough, impurityconcentration removal pipes connected to respective tube means, a valvein each of said pipes for opening and closing the latter, and an orificemeans to which it is connected,

13. In a vapor generator, means providing heating space, combustionmeans for supplying plate in each pipe between its valve and the tubeheatto the space, heating surface formed of tubes, a first part ofsaidheating surface being locatedina portionof saidheatingspace soas toabsorb mainly high intensity radiant heat and a second part of saidheating surface being located in a portion ofsaid heating space so as to,absorb heat of 7 lower intensity transmitted mainly by contact, a pumpfor forcing working medium to flow in, series through the first andsecond parts of the heating surface, the working medium flowingcontinuously and under pressure through the parts of the heating surfacewith continuous absorption of heatso as to continuoualy increase theheat content thereof,.the tubes of said heating surface being sodimensinned and arranged, with respect to operating conditions of saidcombustion means and of said pump, that the zone in which conversion ofmedium from the liquid to the vapor'state is accompanied by highconcentration of scale-forming impurities is located in said second partof the heating surface, and means providing for periodic removal ofimpurity concentrations from said second part of the heating surface.

14. In a vapor generator, means providing heating space; combustionmeans for supplying heat to the space; heating surface formed of tubes;a first part of said heating surface being located in a portion of saidheating space so as radiant heat, a second part of said heating'surfacebeing located in a portion of said heating space so as to absorb ,heatof lower intensity transmitted mainly by contact, and a third part ofsaid heating surface being located in a portion of said heating I spacebetween the first and second parts; a pump for forcing medium to flow inof the heating surface; the working medium flowing continuously andunder pressure through the parts of the heating surface with continuousabsorption of heat so as to increase the heat content thereof; thetubesof said heating sur-* face being so dimensioned and arranged, withrespect to operating conditions of said combusseries through said first,second, and third parts

